The present invention relates to the method for making silicone-polyphenylene graft copolymers by oxidatively coupling a 2,6-dialkylphenol to a monophenol substituted organopolysiloxane macromer. The monophenol substituted organopolysiloxane macromer can be prepared by the hydrosilylation of a phenol having a nuclear bound aliphatically unsaturated radical and a particular monohydrogen organosiloxane.
Prior to the present invention, as shown by copending application, Ser. No. 07/455,122, filed Dec. 22, 1989, silicone-polyphenylene ether graft copolymers were prepared by oxidatively coupling a 2,6-diorganophenol having the formula, ##STR1## to a phenol-siloxane macromer having the formula, ##STR2## where R is selected from a halogen radical, or the same or different C.sub.(1-13) monovalent Organic radicals, R.sup.1 is a C.sub.(2-20) divalent organic radical, R.sup.2 is selected from the same or different C.sub.(1-13) monovalent organic radicals, R.sup.3 is a C.sub.(1-13) monovalent organic radical and n is an integer equal to 1 to 100 inclusive. It has been found that the silicone-polyphenylene ether graft copolymer exhibits outstanding flame retardance and can be employed as a high performance injection moldable thermoplastic.
The phenol-siloxane macromer of Formula 2 can be made by a hydrosilylation addition reaction between an aliphatically unsaturated phenol having the formula, ##STR3## and a hydride terminated polydiorganosiloxane having the formula, ##STR4## where R, R.sup.2, R.sup.3 and n are as previously defined and R.sup.4 is an aliphatically unsaturated C.sub.(2-20) organic radical. The addition between the aliphatically unsaturated phenol of formula (3), and the silicone hydride of formula (4) can be effected with an effective amount of a platinum group metal catalyst, such as platinum.
Radicals included within R of formulas 1 and 2 are, for example, halogen, such as chloro or bormo, C.sub.(1-8) alkyl radicals, such as, methyl, ethyl, propyl and butyl; aryl radicals, such as phenyl, tolyl, xylyl; haloaryl radicals, such as chlorophenyl. Radicals included within R.sup.1 are, for example, C.sub.(2-20) polyalkylene, such as polymethylene, and arylenealkylene, such as phenylenemethylene. Radicals included within R.sup.2, are the same or different radicals included within R. In addition, R.sup.2 can be selected from trifluoropropyl, cyanoethyl and cyanopropyl. Radicals included within R.sup.3 are, for example C.sub.(1-8) alkyl such as methyl, ethyl, propyl and butyl and C.sub.(6-13) aryl, such as phenyl, tolyl and xylyl.
As shown by Ser. No. 07/455,122 the silicone hydride of formula (4) was made by initially lithiating a cyclic diorganosiloxane, such as hexamethyltrisiloxane, with an organollithium compound, for example, butyllithium or phenylithium. The anionic ring opening polymerization of the cyclic trisiloxane has to be conducted under anhydrous conditions.
An alternate route to making monofunctional silicone hydride organosiloxanes of formula (4) is by equilibrating cyclic polydiorganosiloxanes, such as hexaorganotrisiloxane, or octaorganotetrasiloxane with a pentaorgano hydrogensiloxane chainstopper. However, the equilibration route results in the production of a mixture of the desired monofunctional end stopped hydrogen polydiorganosiloxane, as well as polydiorganosiloxane chain terminated with hydride siloxy units on both ends and polydiorganosiloxane free of hydride siloxy end stopped units. Accordingly, if the equilibration mixture containing the desired monofunctional end stopped polydiorganosiloxane along with the other unwanted reaction products is used to make phenol-polyorganosiloxane macromer, as well as silicone-polyphenylene ether graft copolymer by oxidative coupling, a build-up of unreacted polydiorganosiloxane and cross-linked reaction products can result.